Problem: $-\dfrac{3}{10} - \dfrac{4}{6} = {?}$
Solution: $ = - {\dfrac{3 \times 3}{10 \times 3}} - {\dfrac{4 \times 5}{6 \times 5}} $ $ = - {\dfrac{9}{30}} - {\dfrac{20}{30}} $ $ = - \dfrac{{9} - {20}}{30} $ $ = -\dfrac{29}{30}$